Diagnosing heterozygous familial hypercholesterolemia using new practical criteria validated by molecular genetics

Assessment of medical intern's knowledge, awareness and practice of familial hypercholesterolemia at academic institutes in Jeddah, Saudi Arabia

Background

Familial Hypercholesterolemia (FH) is a serious under-diagnosed disease characterized by raised low-density lipoprotein cholesterol (LDL-C) and premature coronary artery diseases (CAD). The scarcity of FH reported patients in Saudi Arabia indicates lack of FH awareness among physicians.

Objective

The goal of this research was to assess knowledge, awareness, and practice (KAP) about FH disorder among Saudi medical interns and to identify areas that need educational attention.

Methods

This cross-sectional study involved 170 Saudi medical interns (83 males and 87 females) from academic institutes in Jeddah, Saudi Arabia. The interns were asked to fill an online FH-KAP questionnaire. Total score for each separate domain measured by adding correct answers.

Results

Although, knowledge of FH definition (76.5%) and classical lipid profile (52.4%) were reasonable; knowledge on inheritance (43.5%), prevalence (12.4%) and CAD risks (7.1%) were poor. Knowledge score was significantly higher in female than male (7.5 ± 3 vs. 5.3 ± 2.6, P < 0.001). Regarding awareness, 54.1% were familiar with FH disorder, 50.6% with the presence of lipid clinic but only 16.5% were acquainted with guidelines. Furthermore, in the practice domain 82.9% selected statin as first line treatment and 62.9% chose routinely checking the rest of the family, while 15.3% chose ages 13–18 years to screen for hypercholesterolemia in patients with a positive family history of premature CAD.

Conclusion

Substantial defects in FH-KAP among Saudi medical interns were found, emphasizing the importance of professional training. Extensive and constant medical education programs as early as an internship are required to close the gap in CAD prevention.

Non-coronary atherosclerotic cardiovascular disease in patients with familial hypercholesterolaemia

Objective: Familial hypercholesterolaemia (FH) is a common autosomal dominant inherited disease, affecting 1 in 200-500 individuals worldwide. FH is characterized by elevated circulating low-density lipoprotein cholesterol (LDL-C) concentrations. Its association with increased risk of coronary heart disease (CHD) (>10-fold, compared with patients without FH) is well documented. However, the association between FH and non-CHD atherosclerotic cardiovascular disease (ASCVD) risk has been poorly documented.Methods: PubMed was searched for English language publications regarding the association between FH and carotid artery stenosis, stroke, peripheral artery disease (PAD; lower limbs and other arterial beds), aortic valve calcification (AoVC), aortic and renal artery disease, chronic kidney disease, atrial fibrillation and heart failure, from conception until 22 December 2019.Results: Despite the small number of available studies, as well as their characteristics (sample size, diagnostic criteria used, retrospective or cross-sectional design), there is evidence for a positive association between FH and stroke, PAD or AoVC. More data are needed for definitive conclusions regarding aortic and renal artery disease, chronic kidney disease, atrial fibrillation and heart failure. There is paucity of data with respect to homozygous FH. Increased lipoprotein (a) concentrations, often seen in FH patients, may also contribute to this non-CHD atherosclerotic process. A key question is whether statins or other LDL-C-lowering therapies, provide an additional reduction in the risk of these less-recognized vascular and non-vascular complications in FH patients.Conclusions: Heterozygous FH is associated with increased risk for stroke, PAD and AoVC. Clinicians should take these non-CHD ASCVD aspects into consideration for optimal management of FH patients.

Incorporation of genetic testing significantly increases the number of individuals diagnosed with familial hypercholesterolemia

BACKGROUND

It is estimated that less than 10% of cases of familial hypercholesterolemia (FH) in the United States have been diagnosed. Low rates of diagnosis may in part be attributable to affected patients not meeting the clinical diagnostic criteria of the Dutch Lipid Clinic Network (DLCN), Simon Broome, or US MEDPED diagnostic criteria.

OBJECTIVE

The objective of this study was to assess the utility of incorporating genetic testing into a patient's evaluation for FH.

METHODS

We retrospectively reviewed patients seen in the Advanced Lipids Disorders Clinic at Johns Hopkins Hospital between January 2015 and May 2018. Between June 2018 and December 2018, patients were consented to a prospective registry. DLCN, Simon Broome, and MEDPED criteria were applied to each patient, before and after genetic testing. Genetic testing included sequencing and deletion duplication analysis of four genes (LDLR, PCSK9, APOB, and LDLRAP1).

RESULTS

The retrospective review and prospective study identified 135 adult probands who were seen in our clinic for evaluation of heterozygous FH. Twenty-nine individuals (21%) were heterozygous for a pathogenic or likely pathogenic monogenic variant. Before genetic testing, using the DLCN criteria, 35 (26%) individuals met criteria for a definite diagnosis of FH. Thirty patients (22%) met criteria using Simon Broome, and 29 (21%) patients met criteria using US MEDPED before genetic analysis. Depending on the criteria, incorporating genetic testing identified 11-14 additional patients with FH.

CONCLUSIONS

Incorporating genetic testing diagnosed almost 50% more patients with definite FH in comparison to classification solely on clinical grounds.

Prognostic value of exercise tolerance test for predicting cardiovascular disease in asymptomatic individuals with heterozygous familiar hypercholesterolemia

Heterozygous familiar hypercholesterolemia (hFH) is an autosomal dominant inherited dyslipidemia, associated with premature cardiovascular disease (CVD). Aim of the study was to define prognostic factors for cardiovascular events (CVE) in asymptomatic individuals with hFH. All participants with recent diagnosis of hFH were recruited from the outpatient lipid clinic from 1987 to 2016, without any previous clinical evidence of CVD. A detailed clinical evaluation and laboratory investigation was obtained. Exercise tolerance test (ETT) was performed until maximum exercise capacity was achieved, without evidence of ischemia. Primary endpoint of the study was the first CVE. Four hundred fifty one participants were followed up for 10 ± 8 years, with 68 recorded cases of CVD (15%). Cumulative incidence of CVD was 15%, 24% and 32% for the 3 decades, respectively. In univariate analysis, male gender (p = 0.016), progression of age (p < 0.001), menopause (p = 0.030), waist-hip ratio (p = 0.043) and increased levels of Lp(α) (p = 0.014) were significantly associated with increased CVD incidence; whereas, exercise capacity (p = 0.025), low variation of heart rate (HR) during all stages of ETT compared to resting state (p = 0.020), maximum systolic (p = 0.014) and diastolic (p < 0.001) blood pressure were inversely associated with CVD. In multi-adjusted analysis, male gender (p < 0.001), duration of ETT (p = 0.023), estimated HR (p = 0.029), variation of HR during ETT compared to resting state (p < 0.05) and maximum diastolic pressure (p = 0.044) were significantly associated with CVD. Parameters of ETT in asymptomatic individuals with hFH, without any evidence of ischemia, may predict CVD in these high-risk patients after decades of observation.

Identifying patients with familial hypercholesterolemia using data mining methods in the Northern Great Plain region of Hungary

BACKGROUND AND AIMS

Familial hypercholesterolemia (FH) is one of the most frequent diseases with monogenic inheritance. Previous data indicated that the heterozygous form occurred in 1:250 people. Based on these reports, around 36,000-40,000 people are estimated to have FH in Hungary, however, there are no exact data about the frequency of the disease in our country. Therefore, we initiated a cooperation with a clinical site partner company that provides modern data mining methods, on the basis of medical and statistical records, and we applied them to two major hospitals in the Northern Great Plain region of Hungary to find patients with a possible diagnosis of FH.

METHODS

Medical records of 1,342,124 patients were included in our study. From the mined data, we calculated Dutch Lipid Clinic Network (DLCN) scores for each patient and grouped them according to the criteria to assess the likelihood of the diagnosis of FH. We also calculated the mean lipid levels before the diagnosis and treatment.

RESULTS

We identified 225 patients with a DLCN score of 6-8 (mean total cholesterol: 9.38 ± 3.0 mmol/L, mean LDL-C: 7.61 ± 2.4 mmol/L), and 11,706 patients with a DLCN score of 3-5 (mean total cholesterol: 7.34 ± 1.2 mmol/L, mean LDL-C: 5.26 ± 0.8 mmol/L).

CONCLUSIONS

The analysis of more regional and country-wide data and more frequent measurements of total cholesterol and LDL-C levels would increase the number of FH cases discovered. Data mining seems to be ideal for filtering and screening of FH in Hungary.

Molecular Characterization of Familial Hypercholesterolemia in a North American Cohort

Background

Familial hypercholesterolemia (FH) confers a very high risk of premature cardiovascular disease and is commonly caused by mutations in low-density lipoprotein receptor (LDLR), apolipoprotein B (APOB), or proprotein convertase subtilisin/kexin type 9 (PCSK9) and very rarely in LDLR adaptor protein 1 (LDLRAP1) genes.

Objective

To determine the prevalence of pathogenic mutations in the LDLR, APOB, and PCSK9 in a cohort of subjects who met Simon Broome criteria for FH and compare the clinical characteristics of mutation-positive and mutation-negative subjects.

Methods

Ninety-three men and 107 women aged 19 to 80 years from lipid clinics in the United States and Canada participated. Demographic and historical data were collected, physical examination performed, and serum lipids/lipoproteins analyzed. Targeted sequencing analyses of LDLR and PCSK9 coding regions and exon 26 of APOB were performed followed by detection of LDLR deletions and duplications.

Results

Disease-causing LDLR and APOB variants were identified in 114 and 6 subjects, respectively. Of the 58 LDLR variants, 8 were novel mutations. Compared with mutation-positive subjects, mutation-negative subjects were older (mean 49 years vs 57 years, respectively) and had a higher proportion of African Americans (1% vs 12.5%), higher prevalence of hypertension (21% vs 46%), and higher serum triglycerides (median 86 mg/dL vs 122 mg/dL) levels.

Conclusions

LDLR mutations were the most common cause of heterozygous FH in this North American cohort. A strikingly high proportion of FH subjects (40%) lacked mutations in known culprit genes. Identification of underlying genetic and environmental factors in mutation-negative patients is important to further our understanding of the metabolic basis of FH and other forms of severe hypercholesterolemia.

Clinical utility of the polygenic LDL-C SNP score in familial hypercholesterolemia

Mutations in any of three genes (LDLR, APOB and PCSK9) are known to cause autosomal dominant FH, but a mutation can be found in only ∼40% of patients with a clinical diagnosis of FH. In the remainder, a polygenic aetiology may be the cause of the phenotype, due to the co-inheritance of common LDL-C raising variants. In 2013, we reported the development of a 12-SNP LDL-C "SNP-Score" based on common variants identified as LDL-C raising from genome wide association consortium studies, and have confirmed the validity of this score in samples of no-mutation FH adults and children from more than six countries with European-Caucasian populations. In more than 80% of those with a clinical diagnosis of FH but with no detectable mutation in LDLR/APOB/PCSK9, the polygenic explanation is the most likely for their hypercholesterolaemia. Those with a low score (in the bottom two deciles) may have a mutation in a novel gene, and further research including whole exome or whole genome sequencing is warranted. Only in families where the index case has a monogenic cause should cascade testing be carried out, using DNA tests for an unambiguous identification of affected relatives. The clinical utility of the polygenic explanation is that it supports a more conservative (less aggressive) treatment care pathway for those with no mutation. The ability to distinguish those with a clinical diagnosis of FH who have a monogenic or a polygenic cause of their hypercholesterolaemia is a paradigm example of the use of genomic information to inform Precision Medicine using lipid lowering agents with different efficacy and costs.

A Belgian consensus strategy to identify familial hypercholesterolaemia in the coronary care unit and its subsequent cascade screening and treatment: BEL-FaHST (The BELgium Familial Hypercholesterolaemia STrategy)

BACKGROUND AND AIMS

Familial hypercholesterolaemia (FH) is an autosomal dominant lipoprotein disorder characterized by significant elevation of low-density lipoprotein cholesterol (LDL-C) and markedly increased risk of premature cardiovascular disease (CVD). Because of the very high coronary artery disease risk associated with this condition, the prevalence of FH among patients admitted for CVD outmatches many times the prevalence in the general population. Awareness of this disease is crucial for recognizing FH in the aftermath of a hospitalization of a patient with CVD, and also represents a unique opportunity to identify relatives of the index patient, who are unaware they have FH. This article aims to describe a feasible strategy to facilitate the detection and management of FH among patients hospitalized for CVD.

METHODS

A multidisciplinary national panel of lipidologists, cardiologists, endocrinologists and cardio-geneticists developed a three-step diagnostic algorithm, each step including three key aspects of diagnosis, treatment and family care.

RESULTS

A sequence of tasks was generated, starting with the process of suspecting FH amongst affected patients admitted for CVD, treating them to LDL-C target, finally culminating in extensive cascade-screening for FH in their family. Conceptually, the pathway is broken down into 3 phases to provide the treating physicians with a time-efficient chain of priorities.

CONCLUSIONS

We emphasize the need for optimal collaboration between the various actors, starting with a "vigilant doctor" who actively develops the capability or framework to recognize potential FH patients, continuing with an "FH specialist", and finally involving the patient himself as "FH ambassador" to approach his/her family and facilitate cascade screening and subsequent treatment of relatives.

New Case Detection by Cascade Testing in Familial Hypercholesterolemia: A Systematic Review of the Literature

BACKGROUND

The prevalence of familial hypercholesterolemia is 1 in 250, but <10% of patients are diagnosed. Cascade testing enables early detection of cases through systematic family tracing. Establishment of familial hypercholesterolemia cascade testing programs in the US could be informed by approaches used elsewhere.

METHODS

We conducted a systematic review of published studies in the English language of cascade testing for familial hypercholesterolemia, which reported the number of index cases and number of relatives tested and specified methods of contacting relatives and testing modalities methods utilized. For each study, we calculated yield (proportion of relatives who test positive) and new cases per index case, to facilitate comparison.

RESULTS

We identified 10 studies from the literature that met inclusion criteria; the mean number of probands and relatives per study was 242 and 826, respectively. The average yield was 44.76% with a range of 30% to 60.5%, and the mean new cases per index case was 1.65 with a range of 0.22 to 8.0. New cases per index case tended to be greater in studies that used direct contact versus indirect contact (2.06 versus 0.86), tested beyond first-degree relatives versus only first-degree relatives (3.65 versus 0.80), used active sample collection versus collection at clinic (4.11 versus 1.06), and utilized genetic testing versus biochemical testing (2.47 versus 0.42).

CONCLUSIONS

New case detection in familial hypercholesterolemia cascade testing programs tended to be higher with direct contact of relatives, testing beyond first-degree relatives, in-home-based sample collection, and genetic testing. These findings should be helpful for establishing cascade testing programs in the United States.

The tertiary hospital laboratory; a novel avenue of opportunistic screening of familial hypercholesterolemia

Background

Familial hypercholesterolemia (FH) is a common monogenic hereditary lipid disorder characterised by increased serum low-density lipoprotein cholesterol (LDL-cholesterol) concentrations and high risk of premature atherosclerotic cardiovascular disease. The prevalence of FH identified in a tertiary hospital laboratory was investigated by performing an opportunistic screen for index cases.

Methods

The prevalence of likely FH based on LDL-cholesterol thresholds >4.9 mmol/L as employed by the Dutch Lipid Clinic Network Criteria (DLCNC) score was evaluated retrospectively in a single tertiary hospital laboratory over a six-month period (July to December 2016).

Results

4943 lipid profiles screened, 106 patients (mean age 53.2 ± 12.9 and 41% male) had LDL-cholesterol of >4.9 mmol/L after exclusion of 5 patients (0.1%) with secondary causes. Possible (n = 90) and probable/definite (n = 16) FH according to DLCNC score was seen in 1.8% and 0.4% of the overall screened population, respectively.

Conclusions

Point prevalence of screening for FH in patients undergoing lipid profile testing in a tertiary hospital laboratory was comparable with prevalence of FH in general population (based on 1 in 200-250). This supports the benefit of establishing an efficient "alert system" in conjunction with a trigger "reflex testing" to facilitate further formal FH scoring and exclusion of possible secondary causes of hyperlipidemia in potential index FH.

Finding missed cases of familial hypercholesterolemia in health systems using machine learning

Familial hypercholesterolemia (FH) is an underdiagnosed dominant genetic condition affecting approximately 0.4% of the population and has up to a 20-fold increased risk of coronary artery disease if untreated. Simple screening strategies have false positive rates greater than 95%. As part of the FH Foundation's FIND FH initiative, we developed a classifier to identify potential FH patients using electronic health record (EHR) data at Stanford Health Care. We trained a random forest classifier using data from known patients (n = 197) and matched non-cases (n = 6590). Our classifier obtained a positive predictive value (PPV) of 0.88 and sensitivity of 0.75 on a held-out test-set. We evaluated the accuracy of the classifier's predictions by chart review of 100 patients at risk of FH not included in the original dataset. The classifier correctly flagged 84% of patients at the highest probability threshold, with decreasing performance as the threshold lowers. In external validation on 466 FH patients (236 with genetically proven FH) and 5000 matched non-cases from the Geisinger Healthcare System our FH classifier achieved a PPV of 0.85. Our EHR-derived FH classifier is effective in finding candidate patients for further FH screening. Such machine learning guided strategies can lead to effective identification of the highest risk patients for enhanced management strategies.

Epicardial fat thickness is significantly increased and related to LDL cholesterol level in patients with familial hypercholesterolemia

PURPOSE

Increased epicardial fat thickness (EFT) is accepted as a risk factfcardiovascular diseases in some studies. There are conflicting results about the relation between plasma low-density lipoprotein cholesterol (LDL-C) level and EFT. As well, the relation between EFT and familial hypercholesterolemia is not clearly documented in the literature. Our aim was to investigate EFT in familial hypercholesterolemia patients and to determine which parameters were related to EFT increase.

METHODS

A total of 150 subjects enrolled in our study. Subjects were separated into two groups: 75 hypercholesterolemia patients (16 men, mean age 52.8 ± 7.4 years) and 75 familial hypercholesterolemia patients (26 men, mean age 50.7 ± 9.2 years). Medical history assessments and complete physical examinations were done. Routine laboratory tests and echocardiographic measurements were performed.

RESULTS

Coronary artery disease frequency was significantly higher in the familial hypercholesterolemia group (p < 0.001). This group had significantly higher TC and LDL-C levels than the hypercholesterolemia group (p < 0.05 for all). EFT values were higher in the familial hypercholesterolemia group, and were significantly different than in the other group (p < 0.001). LDL-C was found to be independently related to EFT in the linear regression analysis.

CONCLUSIONS

Epicardial fat thickness increased in the familial hypercholesterolemia patients. In addition, LDL-C levels were significantly crelated with increased EFT.

Familial hypercholesterolemia in China half a century: A review of published literature

AIMS

To investigate the status of familial hypercholesterolemia (FH) research and the characteristics of patients with FH in China.

METHODS

Published papers in Chinese or English language from PubMed, SinoMed and CNKI databases from 1971 to March 2018 were searched using 'Familial hypercholesterolemia', 'Chinese' and 'Han' as keywords. A systematic review of studies on familial hypercholesterolemia was then conducted.

RESULTS

A total of 391 articles were found, in which 22% were in English and 78% were in Chinese; approximately 43% are case reports and 34% are genetic reports according to the study type; 52% discussed the status of the disease and 11% investigated the subclinical status according to the study content. Furthermore, 96% of the articles were published by tertiary hospitals and 46% were conducted by cardiologists. The first expert consensus was issued in February 2018. Of the 163 case reports published before 2018, 48.7% used the Chinese FH clinical diagnostic criteria and 34.4% did not clearly indicate the diagnostic criteria. The incidence rates of low-density lipoprotein receptor (LDLR) and apolipoprotein B (APOB) mutations were 82% and 9%, and proprotein convertase subtilisin/kexin type 9 (PCSK9) mutations were rare in Chinese patients with FH. However, the data on lipid-lowering treatment rates, compliance rates and cardiovascular events in FH remain insufficient.

CONCLUSIONS

Large-scale epidemiological investigation of FH has not been demonstrated, the recognition of FH remains rudimentary, and the guidelines are incomplete in China. The diagnosis and management of Chinese FH needs to be improved.

Assessment of family physicians' awareness and knowledge of familial hypercholesterolemia in governmental hospitals in Riyadh, Saudi Arabia

Background

Familial Hypercholesterolemia (FH) is an inherited and complex multifactorial disease that can lead to early onset of coronary artery disease (CAD). Diagnosis, treatment, and management of FH require a well-trained physician with high awareness of the disease and different risk factors to avoid complications.

Materials and Methods

This cross-sectional study evaluated family physicians' awareness and knowledge of FH using self-administered questionnaires in governmental hospitals in Riyadh, Saudi Arabia, during 2018.

Results

A total of 225 family physicians completed the questionnaire, with a response rate of 58.4%. The mean age of respondents was 31.3 years and more than 59.1% were men. Although 72.4% of physicians rated their familiarity with FH as average and above, 48.4% of all participants had poor FH knowledge, while only 51.6% had acceptable FH knowledge. About 65.8% of physicians reported that they routinely take a detailed family history, perform a physical examination, and screen close relatives. Awareness of various clinical algorithms for diagnosis of patients with FH was very low at 52.0%. The mean FH knowledge and familiarity scores were significantly higher (P < 0.001) among participants who were older, had higher training levels, or longer years in practice.

Conclusions

The current study revealed significant deficits in FH familiarity, awareness, knowledge, and practice among Saudi physicians. FH educational programs directed at all physicians involved in FH patients' management are necessary to improve physicians' knowledge of all aspects of FH management, including the importance of a mechanism for identifying people at risk for a genetic condition by a process of systematic family tracing.

Improving the detection of familial hypercholesterolaemia

Familial hypercholesterolaemia (FH) is a dominantly inherited disorder of low-density lipoprotein (LDL) catabolism, which if untreated causes lifelong elevated LDL-cholesterol (LDL-c), accelerated atherosclerosis and premature cardiovascular disease. Recent evidence suggests the prevalence of heterozygous FH is ∼1:220, making FH the most common autosomal dominant condition. Lowering LDL-c with statin and lifestyle therapy reduces the risk of cardiovascular events. Furthermore, proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibitors significantly lower LDL-c in addition to statin therapy, and early outcome data suggest improved vascular outcomes with these agents in FH patients in addition to statins. However, the vast majority of people with FH still remain undiagnosed. The onus is on clinicians to identify kindreds with FH, as PCSK9 inhibitors, although expensive, are funded for patients with FH in Australia. Multiple strategies for detecting FH have been proposed. The detection of index cases can be achieved through applying electronic screening tools to general practice databases, universal screening of children during immunisation, and targeted screening of patients with premature cardiovascular disease. Advances in genomic technology have decreased costs of genetic testing, improved the understanding of the pathogenesis of FH and facilitated cascade screening. However, awareness of FH amongst clinicians and the general public still requires optimisation. This review outlines recent advances in FH detection, including emerging strategies and challenges for the next decade.

How well can familial hypercholesterolemia be identified in an electronic health record database?

Background

Familial hypercholesterolemia (FH) is a condition characterized by high cholesterol levels and increased risk for coronary heart disease (CHD) that often goes undiagnosed. The Dutch Lipid Network Criteria (DLNC) are used to identify FH in clinical settings via physical examination, personal and family history of CHD, in addition to the presence of deleterious mutations of the LDLR, ApoB, and PCSK9 genes. Agreement between clinical and genetic diagnosis of FH varies. While an ICD diagnosis code was not available for coding FH until 2016, Systematized Nomenclature of Medicine (SNOMED) clinical concept codes, including genetic diagnoses, for FH have been utilized in electronic health records (EHRs).

Objective

To evaluate the concordance of identifying FH via SNOMED and ICD-10 CM codes vs the DLNC in an EHR database.

Methods

Using the Practice Fusion EHR database, the sensitivity, specificity, positive predictive value (PPV), and negative predictive value were calculated comparing an FH cohort identified via SNOMED and ICD-10 CM codes to one identified via the DLNC.

Results

Among 907,616 patients with hypercholesterolemia, 2,180 were identified as FH via SNOMED code (zero were identified via ICD-10 CM), 259 had a DLNC score 6–8 (probable FH), and 45 had a DLNC score >8 (definite FH). Compared to DLNC score >8, the sensitivity, specificity, and PPV of the FH SNOMED code were 84.4%, 99.4%, and 6.4%, respectively. Compared to DLNC score ≥6, the sensitivity was 36.8% and the specificity was 99.5% with a PPV of 18.7%.

Conclusion

Compared to the clinical criteria for FH, identification of FH patients via SNOMED diagnosis codes had high sensitivity and specificity, but low PPV. The discordance of these two techniques in identifying FH patients speaks to the challenges in identifying FH patients in large electronic databases such as administrative claims and EHR.

Familial Hypercholesterolemia: The Most Frequent Cholesterol Metabolism Disorder Caused Disease

Cholesterol is an essential component of cell barrier formation and signaling transduction involved in many essential physiologic processes. For this reason, cholesterol metabolism must be tightly controlled. Cell cholesterol is mainly acquired from two sources: Dietary cholesterol, which is absorbed in the intestine and, intracellularly synthesized cholesterol that is mainly synthesized in the liver. Once acquired, both are delivered to peripheral tissues in a lipoprotein dependent mechanism. Malfunctioning of cholesterol metabolism is caused by multiple hereditary diseases, including Familial Hypercholesterolemia, Sitosterolemia Type C and Niemann-Pick Type C1. Of these, familial hypercholesterolemia (FH) is a common inherited autosomal co-dominant disorder characterized by high plasma cholesterol levels. Its frequency is estimated to be 1:200 and, if untreated, increases the risk of premature cardiovascular disease. This review aims to summarize the current knowledge on cholesterol metabolism and the relation of FH to cholesterol homeostasis with special focus on the genetics, diagnosis and treatment.

[Screening for familial hypercholesterolemia from low-density lipoprotein cholesterol levels at admission in the coronary care unit]

BACKGROUND

Familial hypercholesterolemia (FH) is a frequent genetic disorder that leads to premature atherosclerosis and coronary artery disease. However, knowledge of FH by cardiologists is weak, and FH remains underdiagnosed in France. FH should be suspected when low-density lipoprotein cholesterol (LDLc) levels exceed 1.9g/L (4.9mmol/L) without lipid lowering therapy.

PURPOSE

This multicenter retro- and prospective observational study aimed at estimating the prevalence of high LDLc levels in patients admitted in coronary care units, and the impact for the personal and familial follow-up for lipid status.

METHODS

Retrospective analysis of all plasma lipid measurements performed at admission in coronary care unit of 4 hospitals in 2017. Retrospective analyses of demographic, clinical, and coronary data of consecutive patients with LDLc levels≥1.9g/L. Prospective 1 year follow-up focused on lipid levels, treatments, and personal and familial screening for FH.

RESULTS

Lipid measurement has been performed in 2172 consecutive patients, and 108 (5%) had LDLc level≥1.9g/L (mean age 64±14 years, men 51%). The primary cause of the hospitalisation was acute coronary syndrome (78%), and 22% of patients were free off coronary artery disease. Lipid lowering therapy was present in 9% of patients at admission, and 84% at discharge, with high statins regimen. At 1-year follow-up, control of LDLc level was not performed in 20% of patients, and statin dose was decreased (36%) or withdrawn (7%) in 43%. Lipid measurement has been performed in at least one first degree relative in 37% of patients, and genetic exploration has been done for 3 patients.

CONCLUSIONS

Screening of FH in CCU should be routinely performed using the Dutch Score when LDLc is above 1.9g/L. Individual and familial management of patients at high risk for FH screened in CCU should be optimized, both for diagnosis and therapeutic purposes.

Recall by genotype and cascade screening for familial hypercholesterolemia in a population-based biobank from Estonia

Purpose

Large-scale, population-based biobanks integrating health records and genomic profiles may provide a platform to identify individuals with disease-predisposing genetic variants. Here, we recall probands carrying familial hypercholesterolemia (FH)-associated variants, perform cascade screening of family members, and describe health outcomes affected by such a strategy.

Methods

The Estonian Biobank of Estonian Genome Center, University of Tartu, comprises 52,274 individuals. Among 4776 participants with exome or genome sequences, we identified 27 individuals who carried FH-associated variants in the LDLR, APOB, or PCSK9 genes. Cascade screening of 64 family members identified an additional 20 carriers of FH-associated variants.

Results

Via genetic counseling and clinical management of carriers, we were able to reclassify 51% of the study participants from having previously established nonspecific hypercholesterolemia to having FH and identify 32% who were completely unaware of harboring a high-risk disease-associated genetic variant. Imaging-based risk stratification targeted 86% of the variant carriers for statin treatment recommendations.

Conclusion

Genotype-guided recall of probands and subsequent cascade screening for familial hypercholesterolemia is feasible within a population-based biobank and may facilitate more appropriate clinical management.

Design of a Controlled Trial of Cascade Screening for Hypercholesterolemia: The (CASH) Study

To inform guidelines for screening family members of patients with familial hypercholesterolemia (FH), we designed a clinical trial to compare the yield of cascade screening in FH patients with and without an identifiable pathogenic variant. Participants with hypercholesterolemia (Low-density lipoprotein cholesterol (LDL-C) > 155 mg/dL) underwent sequencing of LDLR, APOB, and PCSK9 and genotyping of six single nucleotide polymorphisms associated with LDL-C followed by calculation of a polygenic score for LDL-C. We identified 24 patients with definite FH (pathogenic variant in one of the three FH genes), 76 patients with probable FH (Dutch lipid clinic network (DLCN) score ≥ 6, no pathogenic variant), and 262 patients with possible FH (DLCN score 3⁻5, no pathogenic variant). We will enroll 50 patients with definite FH by recruiting an additional 26 from the FH Clinic at Mayo and 50 patients each with probable and possible FH, matching on age and sex. Family members of patients with definite FH will undergo testing for the relevant pathogenic variant using saliva kits and family members of those with probable/possible FH will have a lipid profile checked. We will assess the number of new cases detected (defined as presence of a pathogenic variant in the family member of definite FH patient or LDL-C > 155 mg/dL (>130 mg/dL in children) in family members of probable/possible FH patients, and the cost of detecting a new case. The proposed clinical trial will compare the yield and cost of cascade screening for FH patients with/without an identifiable pathogenic variant, and thereby inform guidelines for cascade screening for FH.

Genetic testing for a patient with suspected familial hypercholesterolaemia

Familial hypercholesterolaemia (FH) is a genetic condition that results in elevated low-density lipoprotein (LDL) cholesterol (LDL-C) levels with consequent increased risk for premature cardiovascular disease events. Although it is considered an autosomal-dominant genetic condition, the underlying genetic causes of FH can be complex. Currently most guidelines rely on clinical criteria to diagnose FH. But this approach has some pitfalls. We present a patient who was not formally diagnosed with FH using commonly used and well-accepted clinical criteria but via genetic testing was found to have a mutation for this disorder. This case brings to fore the challenges clinicians face in diagnosing and managing such unusual cases optimally. Through this case report, we hope to stimulate a debate among clinicians as well as other stakeholders regarding the need to develop more efficient ways of selecting patients for genetic testing in response to elevated LDL levels.

Validation of LDLr Activity as a Tool to Improve Genetic Diagnosis of Familial Hypercholesterolemia: A Retrospective on Functional Characterization of LDLr Variants

Familial hypercholesterolemia (FH) is an autosomal dominant disorder characterized by high blood-cholesterol levels mostly caused by mutations in the low-density lipoprotein receptor (LDLr). With a prevalence as high as 1/200 in some populations, genetic screening for pathogenic LDLr mutations is a cost-effective approach in families classified as ‘definite’ or ‘probable’ FH and can help to early diagnosis. However, with over 2000 LDLr variants identified, distinguishing pathogenic mutations from benign mutations is a long-standing challenge in the field. In 1998, the World Health Organization (WHO) highlighted the importance of improving the diagnosis and prognosis of FH patients thus, identifying LDLr pathogenic variants is a longstanding challenge to provide an accurate genetic diagnosis and personalized treatments. In recent years, accessible methodologies have been developed to assess LDLr activity in vitro, providing experimental reproducibility between laboratories all over the world that ensures rigorous analysis of all functional studies. In this review we present a broad spectrum of functionally characterized missense LDLr variants identified in patients with FH, which is mandatory for a definite diagnosis of FH.

Prediction of subtle left ventricular systolic dysfunction in homozygous and heterozygous familial hypercholesterolemia: Genetic analyses and speckle tracking echocardiography study

BACKGROUND AND AIMS

Few studies have shown the direct effect of familial hypercholesterolemia (FH) on myocardial systolic function. Studies focused on heterozygote FH patients but not homozygote ones, and they did not perform genetic analyses. We aimed to evaluate all types of patients with FH using the potentially more sensitive speckle tracking echocardiography (STE) technique to identify early left ventricular (LV) dysfunction.

METHODS

Genetic analyses of patients with FH were conducted for LDL-receptor, PCSK9, and ApoB100. Nine homozygote, two compound heterozygote, and 82 heterozygote FH patients and 85 healthy subjects were prospectively studied. Longitudinal and circumferential strain measurements and conventional echocardiography findings were obtained.

RESULTS

LV ejection fractions were similar for all (homozygote, heterozygote, and control) groups. The LV average longitudinal strain (aLS) and average circumferential strain (aCS) levels were significantly reduced in the homozygote and heterozygote groups when compared with the controls (for aLS, P = .008 (<.001); for aCS, P =< .001). A significant inverse correlation was found between LDL-C levels and LS (P < .001, r = .728) and CS (P < .001, r = .642) for all FH patients.

CONCLUSIONS

This study demonstrates the potential of using systolic strain values obtained using 2D STE for determining lipotoxicity in the myocardium owing to hypercholesterolemia. Our study found that cardiac functions of homozygote patients who had the highest cholesterol levels were disrupted at very early ages. Therefore, starting lipid reduction treatment and early reverse LV remodelling therapy at early ages may be beneficial for high-risk patients.

Genetic analysis in a compound heterozygote family with familial hypercholesterolemia

Homozygous familial hypercholesterolemia (FH) is rare, with an incidence of ~one in a million and commonly presents with a genetic mutation. The genetic variations of families with FH were clinically analyzed to investigate the association between the phenotype and genotype of patients. Direct sequencing was conducted for the proband and her parents to detect mutations in the fragment of 18 exons of the low‑density lipoprotein receptor (LDLR) and apolipoprotein B100 Q3500R in the peripheral blood genomic DNA. The gene sequences were compared with normal ones to find mutations using GenBank. The QX200 Droplet Digital PCR system was used to detect target DNA copy number variations of the proband and her parents. The functional alterations resulting from the novel mutations were verified by quantitative polymerase chain reaction, western blotting and flow cytometric analyses. The lipid levels of the proband and her parents were all elevated. Genetic testing results indicated that the proband and her mother had a novel heterozygous missense mutation (C377G, 28893T>G) in exon 8 of the LDLR gene, whereas the proband and her father had LDLR gene DNA fragment deletions in exon 18. Clinically, the proband was of a compound heterozygous genotype and her parents were of the simple heterozygous genotype. Furthermore, both mutations led to impaired expression and LDL binding and internalization function of LDLR in vitro. The proband's genotype was confirmed to be compound heterozygous FH, leading to clinical manifestations in line with the homozygous FH phenotype. The phenotype is highly associated with the genotype in this type of compound heterozygous FH.

PCSK9 inhibitors: a non-statin cholesterol-lowering treatment option

Elevated low-density lipoprotein cholesterol (LDL-C) plays a major role in the development of atherosclerotic cardiovascular disease. Statins are the first-line treatment to lower LDL-C in patients with hypercholesterolemia; however, some high cardiovascular risk patients may have inadequate responses to statin therapy or are intolerant to statins, and may need additional and/or alternative non-statin therapies to further reduce their LDL-C levels. Monoclonal antibodies that inhibit proprotein convertase subtilisin/kexin type 9 (PCSK9), a key regulator of circulating LDL-C levels, have received considerable attention as promising non-statin therapeutic options for the management of hypercholesterolemia. This review provides a brief overview of the history and science of PCSK9 inhibitors, focusing on two PCSK9 monoclonal antibodies that have been approved by the US Food and Drug Administration: alirocumab and evolocumab. Recently released and forthcoming clinical trial data will be discussed, as well as the practical application of patient populations that may benefit from PCSK9 inhibitors. Finally, the recent expert recommendations regarding the use of PCSK9 inhibitors and other non-statin therapies to treat patients with inadequate LDL-C-lowering on statin therapy will be summarized.

A Comparative Analysis of Phenotypic Predictors of Mutations in Familial Hypercholesterolemia

CONTEXT

The gold standard for diagnosing familial hypercholesterolemia (FH) is identification of a causative pathogenic mutation. However, genetic testing is expensive and not widely available.

OBJECTIVE

To compare the validity of the Dutch Lipid Clinic Network (DLCN), Simon Broome (SB), Make Early Diagnosis to Prevent Early Deaths (MEDPED), and American Heart Association (AHA) criteria in predicting an FH-causing mutation.

DESIGN, SETTING, AND PATIENTS

An adult cohort of unrelated patients referred to a lipid clinic for genetic testing.

MAIN OUTCOME MEASURES

Odds ratio (OR), area under the curve (AUC), sensitivity, and specificity.

RESULTS

A pathogenic FH-causing mutation was detected in 30% of 885 patients tested. Elevated low-density lipoprotein (LDL) cholesterol and personal or family history of tendon xanthomata were independent predictors of a mutation (OR range 5.3 to 16.1, P < 0.001). Prediction of a mutation for the DLCN and SB definite and MEDPED criteria (ORs 9.4, 11.7, and 10.5, respectively) was higher than with the AHA criteria (OR 4.67). The balance of sensitivity and specificity was in decreasing order DLCN definite (Youden Index 0.487), MEDPED (0.457), SB definite (0.274), and AHA criteria (0.253), AUC being significantly higher with DLCN definite and MEDPED than other criteria (P < 0.05). Pretreatment LDL cholesterol and tendon xanthomata had the highest AUC in predicting a mutation.

CONCLUSIONS

The DLCN, SB, and MEDPED criteria are valid predictors of an FH-causing mutation in patients referred to a lipid clinic, but concordance between these phenotypic criteria is only moderate. Use of pretreatment LDL cholesterol and tendon xanthomata alone may be particularly useful for deciding who should be genetically tested for FH.

Universal Lipid Screening in 9- to 11-Year-Olds Before and After 2011 Guidelines

OBJECTIVE

To determine whether the 2011 guidelines for universal routine screening for dyslipidemia in children aged 9 to 11 years, published by the Expert Panel on Integrated Guidelines for Cardiovascular Health and Risk Reduction in Children and Adolescents and National Heart, Lung, and Blood Institute, are being followed by pediatric primary-care providers.

METHODS

Retrospective data were obtained for 63,951 well-child visits (WCV) in children aged 9 to 11 years from 2 health care systems and 1 insurance program from 2009 to 2015. The proportion of WCV that had a lipid panel or total cholesterol test performed within 1 year of the visit was compared for 2009-2011 versus 2013-2015. Associations between demographic variables and lipid screening were evaluated with logistic regression. The frequency of tested children who had abnormal lipid results was evaluated.

RESULTS

Only 3.5% of 9- to 11-year WCV had lipid tests performed in association with the visit before and after the guidelines. Of those tested, 43% had an abnormal lipid result.

CONCLUSIONS

Utah clinicians rarely follow guidelines for universal lipid screening of children aged 9 to 11. This represents a missed opportunity to identify children at risk for early-onset cardiovascular disease.

Selection of individuals for genetic testing for familial hypercholesterolaemia: development and external validation of a prediction model for the presence of a mutation causing familial hypercholesterolaemia

Aims

Familial hypercholesterolaemia (FH) is an autosomal dominant disease that warrants early diagnosis to prevent premature cardiovascular disease (CVD). However, genetic testing to make a definite diagnosis is costly, and careful selection of eligible subjects is important. Unfortunately, accuracy of current diagnostic criteria is poor, especially in young individuals. We therefore developed and validated a model to predict the presence of an FH causing mutation in persons referred by general practitioners.

Methods and results

All participants in the Dutch FH screening programme from 1994 to 2014 were included in the development cohort. The validation cohort consisted of consecutive patients, suspected for FH, attending the outpatient lipid clinic in Saguenay (Quebec) from 1993 to 2014. Cross-sectional data were available on medical history, lipid profile, and DNA analysis. Multivariable logistic regression analysis was used for model development. The primary outcome was the presence of a deleterious FH mutation. The development cohort comprised 26 167 FH patients and 37 939 unaffected relatives. Our final model included age; sex; levels of low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol, and triglycerides; history and age of CVD; use of statins; smoking; alcohol; and presence of hypertension. The area under the receiver operating characteristic curve (AUC) was 85.4% (95% CI: 85.0-85.9). The calibration slope was 1.02 (where 1.00 is optimal). In the validation cohort (1436 FH patients and 1767 unaffected persons), the AUC was 95.4% (95% CI: 94.7-96.1%) and the calibration slope 1.06.

Conclusion

Our model showed good discrimination and calibration. We specifically expect our model to be of added value for young persons set against current diagnostic criteria, since LDL-C and age are now used as continuous predictors. The equation will be available as an online calculator to estimate the probability of the presence of an FH mutation in individual patients. This tool might aid physicians in the decision for referral of patients for molecular testing.

Imputation of Baseline LDL Cholesterol Concentration in Patients with Familial Hypercholesterolemia on Statins or Ezetimibe

BACKGROUND

Familial hypercholesterolemia (FH) is the most frequent genetic disorder seen clinically and is characterized by increased LDL cholesterol (LDL-C) (&gt;95th percentile), family history of increased LDL-C, premature atherosclerotic cardiovascular disease (ASCVD) in the patient or in first-degree relatives, presence of tendinous xanthomas or premature corneal arcus, or presence of a pathogenic mutation in the LDLR, PCSK9, or APOB genes. A diagnosis of FH has important clinical implications with respect to lifelong risk of ASCVD and requirement for intensive pharmacological therapy. The concentration of baseline LDL-C (untreated) is essential for the diagnosis of FH but is often not available because the individual is already on statin therapy.

METHODS

To validate a new algorithm to impute baseline LDL-C, we examined 1297 patients. The baseline LDL-C was compared with the imputed baseline obtained within 18 months of the initiation of therapy. We compared the percent reduction in LDL-C on treatment from baseline with the published percent reductions.

RESULTS

After eliminating individuals with missing data, nonstandard doses of statins, or medications other than statins or ezetimibe, we provide data on 951 patients. The mean ± SE baseline LDL-C was 243.0 (2.2) mg/dL [6.28 (0.06) mmol/L], and the mean ± SE imputed baseline LDL-C was 244.2 (2.6) mg/dL [6.31 (0.07) mmol/L] (P = 0.48). There was no difference in response according to the patient's sex or in percent reduction between observed and expected for individual doses or types of statin or ezetimibe.

CONCLUSIONS

We provide a validated estimation of baseline LDL-C for patients with FH that may help clinicians in making a diagnosis.

Genetic Architecture of Familial Hypercholesterolaemia

PURPOSE OF REVIEW

Familial hypercholesterolaemia (FH) is an inherited disorder of low-density lipoprotein cholesterol (LDL-C) which is characterised by a raised cholesterol level from birth and a high risk of premature coronary heart disease. In this paper, we review the genetic basis of FH and its impact on the clinical presentation.

RECENT FINDINGS

Mutations in any of three genes (LDLR, APOB and PCSK9) are known to cause autosomal dominant FH, but a mutation can be found in only ∼40% of patients with a clinical diagnosis of FH. In the remainder, a polygenic aetiology is most likely, due to the co-inheritance of common LDL-C-raising variants. The cardiovascular presentation and management of FH will differ between patients based on their underlying genetic factors. New genotyping methods such as next-generation sequencing will provide us with better understanding of the genetic architecture of FH.

Spectrum of mutations in index patients with familial hypercholesterolemia in Singapore: Single center study

BACKGROUND AND AIMS

Familial hypercholesterolemia (FH) is an autosomal dominant genetic disease characterized by the presence of high plasma low density lipoproteins cholesterol (LDL-c). Patients with FH, with mutation detected, are at increased risk of premature cardiovascular disease compared to those without mutations. The aim of the study was to assess the type of mutations in patients, clinically diagnosed with FH in Singapore.

METHODS

Patients (probands) with untreated/highest on-treatment LDL-c>4.9 mmol/l were recruited (June 2015 to April 2017). Anthropometric, biochemical indices, blood and family history were collected. DNA was extracted and Next Generation Sequencing (NGS) was performed in 26 lipid-related genes, including LDLR, APOB and PCSK9, and validated using Sanger. Multiplex-ligation probe analyses for LDLR were performed to identify large mutation derangements. Based on HGVS nomenclature, LDLR mutations were classified as "Null"(nonsense, frameshift, large rearrangements) and "Defective"(point mutations which are pathogenic).

RESULTS

Ninety-six probands were recruited: mean age: (33.5 ± 13.6) years. 52.1% (n = 50) of patients had LDLR mutations, with 15 novel mutations, and 4.2% (n = 4) had APOB mutations. Total cholesterol (TC) and LDL-c were significantly higher in those with LDLR mutations compared to APOB and no mutations [(8.53 ± 1.52) vs. (6.93 ± 0.47) vs. (7.80 ± 1.32)] mmol/l, p = 0.012 and [(6.74 ± 0.35) vs. (5.29 ± 0.76) vs. (5.98 ± 1.23)] mmol/l, p=0.005, respectively. Patients with "null LDLR" mutations (n = 13) had higher TC and LDL-c than "defective LDLR" mutations (n = 35): [(9.21 ± 1.60) vs. (8.33 ± 1.41)]mmol/l, p = 0.034 and [(7.43 ± 1.47) vs. (6.53 ± 1.21)]mmol/l, p=0.017, respectively.

CONCLUSIONS

To our knowledge, this is the first report of mutation detection in patients with clinically suspected FH by NGS in Singapore. While percentage of mutations is similar to other countries, the spectrum locally differs.

Familial hypercholesterolaemia

Familial hypercholesterolaemia is a common inherited disorder characterized by abnormally elevated serum levels of low-density lipoprotein (LDL) cholesterol from birth, which in time can lead to cardiovascular disease (CVD). Most cases are caused by autosomal dominant mutations in LDLR, which encodes the LDL receptor, although mutations in other genes coding for proteins involved in cholesterol metabolism or LDLR function and processing, such as APOB and PCSK9, can also be causative, although less frequently. Several sets of diagnostic criteria for familial hypercholesterolaemia are available; common diagnostic features are an elevated LDL cholesterol level and a family history of hypercholesterolaemia or (premature) CVD. DNA-based methods to identify the underlying genetic defect are desirable but not essential for diagnosis. Cascade screening can contribute to early diagnosis of the disease in family members of an affected individual, which is crucial because familial hypercholesterolaemia can be asymptomatic for decades. Clinical severity depends on the nature of the gene that harbours the causative mutation, among other factors, and is further modulated by the type of mutation. Lifelong LDL cholesterol-lowering treatment substantially improves CVD-free survival and longevity. Statins are the first-line therapy, but additional drugs, such as ezetimibe, bile acid sequestrants, PCSK9 inhibitors and other emerging therapies, are often required.

ASPECTS OF DETECTING PATIENTS WITH FAMILY HYPERCHOLESTEROLEMIA

The review presents current data regarding the etiology and epidemiology of familial hypercholesterolemia (FH), algorithms for identifying patients with FH using clinical scales, genetic testing, cascade screening. The current tactics of treatment of family hypercholesterolemia, including in children and pregnant women, are given.

Anti-PCSK9 antibodies for the treatment of heterozygous familial hypercholesterolemia: patient selection and perspectives

Heterozygous familial hypercholesterolemia (FH) is a genetic disorder characterized by high low-density lipoprotein cholesterol levels from birth, which exposes the arteries to high levels of atherogenic lipoproteins lifelong and results in a significantly increased risk of premature cardiovascular events. The diagnosis of FH, followed by an appropriate and early treatment is critical to reduce the cardiovascular burden in this population. Phase I–III clinical trials showed the benefit of proprotein convertase subtilisin kexin 9 inhibitors, both alirocumab and evolocumab, in these patients with an average low-density lipoprotein cholesterol reduction ranging from −40% to −60%. The aim of this review is to address the unmet needs in cholesterol management, elucidate the biology and the clinical benefit of proprotein convertase subtilisin kexin 9 inhibition and finally discuss the open gaps and future directions in the treatment of patients with heterozygous FH.